In the beginning…

Most ancient cultures recognized seven “planets”
consisting of sun and moon and the five planets[1]
visible in the sky. The Latin names of the Planets were simple translations of
the Greek names, which in turn were translations of the Babylonian names, which
go back to the Sumerians. Some interpretation was required for the Greek, and
even for the Babylonian, translations, however. Nergal, for instance, was the
god of war but also of pestilence and, especially, the Underworld
—overlapping with the Greek Hades. While Kronos was the father of Zeus,
Ninurta was the son of Enlil. The Babylonians replaced the Sumerian national
gods Enlil and Enki with the patron god of Babylon, Marduk, and his son, Nabě
— though Marduk was actually taken to be the son of Enki (called Ea in Babylonian). Ninurta, an obscure
god inherited by the Babylonians, may have been identified with Saturn, the
slowest moving visible planet, because, at least in one story, he was
identified with the turtle. The ancient Egyptian, Sanskrit, and Chinese names
for the planets are unrelated to the Sumerian.

The Ancient “Planets”:

English

Sumerian

Babylonian

Greek

Latin

Egyptian

Sanskrit

Moon

Nanna

Sin

Selenź

Luna

Aah or Iah

Chandra

Mercury

Enki

Nabě

Hermes

Mercurius

Sabgu

Budha

Venus

Inanna

Ishtar

Aphroditź

Venus

Ba’ah or
Seba-djai

Sukra

Sun

Utu

Shamash

Helios

Sol

Aten

Surya

Mars

Gugulanna

Nergal

Ares

Mars

Heru-deshet

Mangala

Jupiter

Enlil

Marduk

Zeus

Iuppiter

Her-wepes-tawy

Brhaspati

Saturn

Ninurta

Ninurta

Kronos

Saturnus

Sani

The Chinese[2]
names for the true planets are derived from the five elements. The Japanese and
Vietnamese probably derived their names for the planets from the Chinese (The
Japanese characters are essentially identical to the Chinese although the
pronunciation rendered here differs considerably). The Vietnamese word Sao means “star”.

English translation

Mandarin Chinese

Japanese

Vietnamese

water star (Mercury)

shui3-xing1

suisei

Sao Thuy

metal star (Venus)

jin1-xing1

kinsei

Sao Kim

fire star (Mars)

huo3-xing1

kasei

Sao Hoa

wood star (Jupiter)

mu4-xing1

mokusei

Sao Moc

earth star (Saturn)

tu3-xing1

dosei

Sao Tho

The Chinese also had an earlier set of names from
which the Japanese and Vietnamese also derived their earlier names for the
planets.

English

Chinese

Japanese

Vietnamese

Mercury

Chen2-xing1

Shinsei

Thąn tinh

Venus

Tai4-bai2-xing1

Taihakusei

Sao thái bach

Mars

Ying2-huo4

Keiwaku

Huynh Hoac

Jupiter

Sui4-xing1

Saisei

Tue tinh

Saturn

Zhen4-xing1

Chinsei

Tran tinh

Ad Astra

Aristarchos of Samos developed an essentially correct
theory of a sun-centered solar system surrounded by distant stars, “suns like
our own,” in the 3rd century BCE, but his ideas were ignored and mostly
forgotten for 2000 years.* Then, in
the 17th century, great minds like Copernicus, Galileo, and Kepler
came to the same conclusions about the true relationships of earth, sun, moon,
planets, and stars. With the discovery that the earth orbits the sun, the solar
system became, at the same time, simpler and more complex. First, the sun and
moon had to be removed from the list of planets and the earth added to it.
Then, Sir William Herschel and his sister, Caroline, found Uranus in 1780;
Johann Galle and Heinrich D’Arrest discovered Neptune in 1846; and Clyde Tombaugh
discovered Pluto in 1930. The International Astronomical Union (IAU) is the
body that officially assigns names to celestial objects and continued the
tradition of naming the planets for Roman deities for the three “modern”
discoveries.

Different languages either use transliterations of
the IAU names for the three modern planets or use translations of the official
names. Chinese, Vietnamese, and Japanese, for example, use translations. They
are:

Translation

Chinese

Vietnamese

Japanese

King of Heaven (Uranus)

Tian1 wang2
xing1

Sao Thiźn Vúóng

Tennoosei

King of the Sea (Neptune)

Hai3 wang2 xing1

Sao Hai Vúóng

Kaioosei

King of the Netherworld (Pluto)

Ming2 wang2 xing1

Sao Diźm Vúóng

Meioosei

Modern telescopes have discovered planets orbiting
other stars and have discovered several bodies orbiting our sun in the Kuiper
Belt beyond Pluto. But, oddly enough, there was no official scientific
definition of a planet until 2005. The Kuiper Belt discoveries, along with
Pluto’s diminutive size, led the IAU to adopt a formal definition of “planet”
at their convention in 2005. Here is the IAU resolution:

The IAU...resolves that planets and
other bodies, except satellites, in our Solar System be defined into three
distinct categories in the following way:

(1) A planet is a celestial body
that (a) is in orbit around the Sun, (b) has sufficient mass for its
self-gravity to overcome rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around
its orbit.

(2) A “dwarf planet” is a celestial
body that (a) is in orbit around the Sun, (b) has sufficient mass for its
self-gravity to overcome rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around
its orbit, and (d) is not a satellite.

(3) All other objects, except
satellites, orbiting the Sun shall be referred to collectively as “Small Solar
System Bodies”.

(Subsequent debates have clarified that “cleared the neighbourhood around its orbit” refers to the process
that happened during the formation of the planets and does not refer to the
presence of bodies that later strayed into the orbit after the accretions took
place. This interpretation was necessary to resolve the conflict that “if Pluto
is not a planet because it has not “cleared its neighbor hood”, then neither is
Neptune (because it has not cleared Pluto from its orbital neighborhood) nor
Jupiter with the 100,000 or so Trojan asteroids in its orbit nor is the Earth
with more than 10,000 near-earth asteroids and other objects in its orbital
neighborhood)

The most immediate effect of the new definition was
to remove Pluto from the list of solar planets. The howls of protest have not
died down, and new discoveries will almost certainly make the new definition
obsolete and require its revision. Many of the flaws in the definition have
already been identified, among them:

ŠThe definition is far too narrow. It applies
only to the bodies in our solar system and does not entirely agree with the accepted
criteria for defining extrasolar planets.

ŠThere is no provision for “rogue” planets (those
planet-type objects cast out of systems and now free of any star)

ŠThe definition is largely depends on assumptions about how a body is formed
whereas the facts are unknown.

oIdentifying
whether an asteroid was captured or is a left-over from accretion remains
“iffy” — largely a matter of many assumptions and guesswork. This is not a
good basis for science.

oThe
latest data from the Stardust mission indicates that planetary formation is far
from the neatly organized affair upon which the new definition is based.

[1] Actually, with clear dark
skies, seven planets are visible to the unaided eye if you know where to look,
but Uranus and Neptune are so faint that they are easily missed among the
stars. Only distant Pluto is truly not visible to the unaided eye; seeing it
requires a telescope of at least eight inches aperture and excellent
atmospheric conditions. Of course, the Ancients did not count the earth as one
of the planets. It was under their feet and fixed (so they thought) and,
therefore, not a “wanderer” (the meaning of planet)
in the heavens.

[2]The European transliteration used here for Mandarin Chinese
is pinyin. The tonal inflections are indicated by a number at the end of the
syllable, thus: 1First tone: high and
flat2Second tone: rising 3Third tone: low falling
then rising4Fourth tone: falling.

*Aristarchos’ theory was never entirely
forgotten. Although it was eventually pushed aside by Ptolemy’s meticulously
measured earth-centered system that held sway until Copernicus and Galileo,
Aristarchus’ theory was accepted by many learned people for some centuries
after it was written; witness the following written by the poet Cicero in the
first century BCE:

“Each
has been given a spark from these eternal fires which you call stars and
planets, which are globular and rotund and are animated by divine intelligence,
and which with marvelous velocity revolve in their established orbits.”
— M. Tullius Cicero (106–43 BCE)